This invention relates generally to apparatus used in drilling lateral wells from vertical wells, for purposes of producing oil and gas from subsurface formations.
Since its usage began, horizontal drilling has offered dramatic reservoir-exposure improvements. Lately, a new trend has developed towards drilling multiple laterals, thus further increasing production. Until recently, laterals typically were not cased and tied back, which meant when workovers or cleanouts were required, reentry was difficult and completions were virtually impossible.
Now, the technology allows multiple laterals to be cased and tied back. Multilaterals may be drilled into predetermined producing-formation quadrants at any time in the productive life cycle of wells and can be used in vertical, directional or horizontal applications.
Minimizing the distance hydrocarbons must travel to the wellbore is an important goal. One surface hole installation can now incorporate an integral casing drainage system that takes the wellbore to the hydrocarbons in place.
The same directional bottomhole assembly used to initiate the kickoff is used to drill the build or turn portion of the lateral wellbore. Once a lateral has been drilled, a secondary liner and hanger system is placed into the newly drilled wellbore and mechanically tied back to the main casing string, allowing future re-entry into the new leg. The deflection device can immediately be moved to the next window joint upon installation of the lateral string.
Either the drilling cycle can commence on the next lateral, or the deflection device can be retrieved to surface, enabling access to all casing strings. The deflection device can, alternatively, be left on bottom, to be available if additional laterals are drilled at some other time, to further improve reservoir recovery based on performance of the original wellbore and its added lateral or laterals.
Additional benefits are that the system creates a natural separator for oil and gas production in vertical applications, and it creates the opportunity to drill, complete and produce from several different formations tied to one surface-hole casing string.
An integral part of the system for drilling either a single lateral well, or a multiple lateral well scenario, is the so-called casing window joint, a joint of steel casing having a pre-cut or pre-formed window which is easily drillable. The casing window system is available in various oilfield-tubular material grades. The completed casing window is then overwrapped with composite materials (similar to fiberglass).